They cost so much because of the materials put in and the dangerousness into them.
The $100-$150 is actually more than it costs to fabricate in my opinion.
Then the commercial adding which is added by the shop comes in, and the VAT.
Eitherway, the swords are actually overpriced comparing to materials. But to legallity, it is just fine.
The katanas sold are not intended for fighting but for decorations.